class_docstr: Basic interface for SAX error handlers.
  
  If you create an object that implements this interface, then
  register the object with your XMLReader, the parser will call the
  methods in your object to report all warnings and errors. There
  are three levels of errors available: warnings, (possibly)
  recoverable errors, and unrecoverable errors. All methods take a
  SAXParseException as the only parameter.
docstr: Handle a warning.
docstr_tok: ["Handle","a","warning","."]
code: def warning(self, exception):
      "Handle a warning."
      print(exception)
  
label_desc: Use image node_id 3 for calling the ErrorHandler obj's underlying member method code with example usage: obj.warning(exception) without return types